Conventional articles of athletic footwear generally include two primary elements, an upper and a sole structure. The upper is secured to the sole structure and forms a void on the interior of the footwear for comfortably and securely receiving a foot. The sole structure is secured to a lower portion of the upper and is positioned between the foot and the ground. The sole structure generally incorporates multiple layers that are conventionally referred to as an insole, a midsole, and an outsole. The insole, or sockliner, is a thin, compressible member located within the void and proximate a lower surface of the foot to enhance footwear comfort.
The outsole forms a ground-engaging portion (or other contact surface-engaging portion) of the sole structure, and is formed from a durable and wear-resistant material that includes texturing to improve traction.
To keep a wearer safe and comfortable, footwear is called upon to perform a variety of functions. For example, the sole structure of footwear should provide adequate support and impact force attenuation properties to prevent injury and reduce fatigue, while at the same time provide adequate flexibility so that the sole structure articulates, flexes, stretches, or otherwise moves to allow an individual to fully utilize the natural motion of the foot.
The midsole, which is conventionally secured to the upper along the length of the upper, forms a middle layer of the sole structure and is primarily responsible for attenuating ground (or other contact surface) reaction forces to lessen stresses upon the foot and leg, may also beneficially utilizing such ground reaction forces for more efficient toe-off, and control potentially harmful foot motions, such as over pronation. Conventional midsoles may include a foam material to attenuate impact forces and absorb energy when the footwear contacts the ground during athletic activities. Other midsoles may utilize fluid-filled bladders (e.g., filled with air or other gasses) to attenuate impact forces and absorb energy.
It would be desirable to provide an article of footwear with a forward displacement assembly that reduces or overcomes some or all of the difficulties inherent in prior known devices. Particular advantages will be apparent to those skilled in the art, that is, those who are knowledgeable or experienced in this field of technology, in view of the following disclosure of the invention and detailed description of certain embodiments.